Docker layers and build cache efficiency
WHAT IT TESTS: layer/union FS and caching. OUTLINE: each instruction makes a content-addressed read-only layer stacked by a union FS; shared layers are pushed/pulled once, and ordering the Dockerfile so volatile steps come last maximizes cache reuse.
WHAT IT TESTS: understanding layers, content addressing and cache ordering. ANSWER OUTLINE: each Dockerfile instruction produces an immutable, content-addressed layer; a union filesystem stacks them with a writable top layer at runtime. Registries deduplicate by digest, so unchanged shared layers transfer only once. In builds, order instructions so rarely changing steps like dependency installs come before frequently changing ones like copying source, and any changed layer invalidates all below it.
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- #docker
- #layers
- #build-cache
- #ci-cd
- #overlayfs
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